Various prosthetic occluders for repairing intracardiac defects, such as interatrial and interventricular septal shunts, patent ductus arteriosus and aortic-pulmonary window have been proposed by the prior art. Representative is U.S. Pat. No. 3,874,388 to King et al. which discloses a device including a pair of opposed umbrella-like occluder elements which lock together at a central hub extending across the defect.
The King patent describes an assembly for percutaneous transluminal delivery of the umbrella-like occluder including a delivery cone, a catheter and an obturator guidewire. The distal end of the delivery cone is inserted in to the proximal end of the catheter and includes a cone-shaped lumen which compresses the occluder as it is advanced from the delivery cone to the catheter lumen in a procedure known as "front-end loading". The obturator guidewire extends through the delivery cone and the catheter lumen and is threaded at a distal tip to the occluder. Manipulation of the proximal end (outside of the patient) of the obturator wire reciprocally advances the collapsed umbrella-like occluder transluminally to the septal or ductus defect. Unscrewing the distal tip of the obturator wire, by rotating the proximal end, releases the deployed umbrella-like occluder from the delivery system.
A prosthetic occluder delivery system is described in W. J. Rashkind et al., "Non Surgical Closure of Patent Ductus Arterious: Clinical Application of the Rashkind PDA Occluder System," Circulation, Vol. 75, No. 3, March 1987, pg. 583-592. The Rashkind rear-end loading delivery system 500 illustrated in FIG. 1 includes a delivery assembly 501 and a separate loading device 502 for collapsing and then rear-end loading the collapsed occluder into the delivery assembly 501. The delivery assembly 501 includes an 85 cm long 8 French catheter 504, a delivery wire 506 and a locking wire 508. The distal tip of the catheter 504 includes a metal tubular pod 510 having a central lumen sized to maintain the occluder in the collapsed configuration. The delivery wire 506 and the locking wire 508 extend through the catheter 504 and beyond the pod 510. An attachment eye 512 extending from the occluder is seatable about a hemispherical-shaped knuckle 514 at the distal end of the locking wire 508. The lumen of a metal sleeve 516 at the distal end of the delivery wire 506 is sized to prevent the detaching of the knuckle 514 and attachment eye 512. The delivery wire 506 and locking wire 508 are axially moveable relative to one another and to the metal sleeve 516 by manipulation of a piston-cylinder control handle 518. A back bleed gasket assembly 520 at the proximal end of the catheter includes a side leg 522 for infusing liquid along the entire length of the catheter 504 and through the pod 510 to aspirate air bubbles from the compressed occluder.
The Rashkind procedure for loading the occluder, known as "rear-end loading", begins with the connection of the proximal occluder element 524 to the delivery assembly 501. The knuckle 514 is advanced distally of the metal sleeve 516 by closing the control handle 518. The attachment eye 512 is placed around the knuckle 514 so that the occluder elements 524, 526 are perpendicular to the longitudinal axis of the catheter 504. Extension of the control handle 518 draws the seated attachment eye 512 and knuckle 514 into the metal sleeve 516.
Tension applied to the sutures 528 extending through the loading device 502 causes the distal occluder element 524 to fold into the conical portion 530. As the sutures 528 are pulled through the loading device 502, the following proximal occluder element 26 folds backwards and is drawn into the conical portion 530. The occluder is pulled through the loading device 502 until it completely collapses in the distal portion 532. The pod 510 is advanced over the delivery wire 506 into the middle section 533 of the loading device 502. After cutting the sutures, the delivery wire is retracted which in turn draws the collapsed occluder completely into the pod 510. After removing the pod 510 from the loading device 502, the rear-end loaded collapsed occluder is flushed by infusing liquid from the side leg 522 all the way down the catheter 504 and through the pod 510. The flushed delivery assembly 501 is inserted into an already emplaced introducer sheath and then the pod 510 is transluminally advanced towards the defect.
The Rashkind rear-end loading system suffers from several deficiencies. It requires coordination of a separate loading cone and delivery assembly to collapse the occluder and then deliver the collapsed occluder into the introducer sheath. Handling of the lengthy and thick delivery catheter is awkward. Aspiration and flushing of the occluder has proved inefficient because the infusion fluid must be injected 85 cm downstream of the collapsed occluder. Mating of the attachment eye and knuckle, which is required to connect the occluder to the delivery system, requires a practiced skill and may take several attempts even for the experienced physician. Further, the rigidity of the metal pod precludes the delivery system from being navigated along the twisted curvature of the blood vessels adjacent the defect site and therefore prevents the delivery system from transporting the occluder to the defect site.
Accordingly, the prior art lacks a compact and efficient system for collapsing, flushing and then delivering a prosthetic occluder to a defect site.